Abyssal-mixing driven circulation in the Antarctic Circumpolar Current

The MITGeneral Circulation Model (MITgcm) is configured to simulate a circumpolar current in a mesoscale eddy-resolving zonal channel. Lee waves are generated, calculated from the model stratification, velocities and prescribed sub-grid-scale topography following nonlinear internal lee wave theory. The energy input that arises from breaking of these lee waves is parameterised via a vertical diffusivity profile, estimated online from the internal lee wave energy generation rate. A vigorous but bottom-trapped residual abyssal circulation is found to be forced by this mixing. Scaling arguments are adduced to explain it strength, which is found to be sensitive to the meridional temperature gradient and bottom velocities of the large scale flow, the topographic roughness, and the isopycnal eddy excursions (linked to the deep tempearture variance and the stratification).